US5119466A - Control motor integrated with a direct current motor and a speed control circuit - Google Patents

Abstract

A control motor comprising an integrated direct current motor and speed control circuit, the speed control circuit controlling a rotational speed of the direct current motor by means of changing a voltage applied to an armature by a chopping of a switching element, the speed control circuit being composed upon a printed circuit board, the printed circuit board being supported in the direct current motor by a case member formed of a heat-conducting material, and a radiation portion of the switching element which is closely contracted with a projection formed integrally with the case member and is installed in the projection.

Description

BACKGROUND OF THE INVENTION

The invention relates to a control motor comprising an integrated direct current motor and speed control circuit and, more particularly to a control motor which is suitable for use as a blower motor provided in a vehicle air conditioner and an electrically-driven fan motor for cooling a radiator.

In the vehicle air conditioner a rotational speed of the blower motor is controlled in order to regulate air flow blown in a vehicle compartment.

In some of the speed control circuits of this kind, the rotational speed of the blower motor is controlled linearly by a power transistor. The advantage of linear control is that little noise is generated; the disadvantage to linear control, however, is that heat is generated in the power transistor. The Japanese Patent Application No. 235114 of 1988 discloses anintake unit 110, in which aswitching element 113 installing aheat sink 112 is positioned near ascroll 111 of theintake unit 110 to radiate the heat, as illustrated in FIGS. 29 and 30.

The Japanese Patent Application No. 235114 of 1988 also discloses theintake unit 110, in which a voltage is controlled by a chopping performed by a pulse width modulation control (PWM control) to control generation of heat in the speed control circuit and a power MOSFET generating only a little heat is used as the switching element. In such a motor as disclosed in the Japanese Patent Application No. 235114 of 1988, there is a relatively little heat generated in the speed control circuit and radiating the heat is easy, therefore the speed control circuit is placed in a motor bracket to be formed integrally with the direct current motor, leading to an easy installation of the direct current motor. This control motor comprised of the integrated direct current motor and the speed control circuit is referred to as a smart motor or an intelligent motor.

The speed control performed by the chopping has a disadvantage in that radio frequency noise is generated by the speed control circuit. In a motor loaded into the vehicle a power source is a battery and the voltage is low. Further, in a large motor, a high current of more than 30A must be switched. In this switching, a float inductance and a float capacitance of the speed control circuit produce a voltage and a current oscillation of a far higher frequency than the switching frequency, generating radio frequency noise. The radio frequency noise may conduct to other electronic apparatuses connected with the same battery with the radio via the power line, producing harmful influences such as faulty operation of a microcomputer. Further, the noise is radiated directly as an electromagnetic wave, exerting a harmful influence on electronic apparatuses provided in a periphery of the radio. Also, the noise intrudes from an antenna of a radio loaded in a vehicle, preventing receipt of the radio frequency from a broadcasting station. In a conventional control motor having a speed control function and using a high current, no consideration was given to the above radio noise.

SUMMARY OF THE INVENTION

An object of the invention is to provide a control motor comprising an integrated direct current motor and a speed control circuit which reduces the radio frequency noise generated by switching.

Another object of the invention is to provide a control motor comprising an integrated direct current motor and a speed control circuit which improves the radiation of heat produced by a switching element.

To attain the above objects, as illustrated in FIG. 1, there is provided in the invention the control motor comprising an integrated direct current motor and speed control circuit, the speed control circuit controlling a rotational speed by changing a voltage applied to an armature by a chopper, the control motor characterized in that a printed-circuit board 40, upon which is composed the speed control circuit is supported in the direct current motor by alower case member 34 formed of a material which conducts heat and electricity well and a radiation portion of aswitching element 9 is closely contacted with aprojection 41 formed integrally with thelower case member 34 and is installed in theprojection 41.

It is desired, as illustrated in FIGS. 8 and 9, that the printedcircuit board 40 have through-hole conductors 58 and 59 conducting to aground pattern 57 and the printed circuit board to be installed in thelower case member 34 by a conductive metallic installing means ofscrews 36 and 37 or a rivet inserted into the through-hole conductors 58 and 59.

Further, it is desired, as illustrated in FIG. 10, FIG. 21, and FIG. 22, that thelower case member 34 be kept conducting electrically to theground pattern 57 and be fixed in a yoke of the directcurrent motor 5 by a metallic fixing means ofscrews 60 and 97 or arivet 98.

In the control motor comprising a direct current motor and speed control circuit which is constructed as above, thelower case member 34 is formed of the material which conducts heat and electricity well. Therefore, thelower case member 34 formed integrally with theprojection 41 performs a function of a heat sink for theswitching element 9. Also, because thelower case member 34 is formed of the material which conducts heat and electricity well, thelower case member 34 also performs a function of an electromagnetic shield which shields electromagnetic noise generated by the printedcircuit board 40.

In the control motor in which the printedcircuit board 40 is installed by the through-hole conductors 58 and 59, grounding and securing thelower case member 34 is facilitated and the electromagnetic shield function of the lower case member is heightened.

In the control motor in which thelower case member 34 is fixed in the yoke of the direct current motor by the metallic fixing means of thescrews 60 and 97 or therivet 98, the electromagnetic shield function of the direct current motor yoke is heightened by grounding the direct current motor yoke.

Other and further objects, features and advantages of the invention will become appear more fully from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 16 illustrate a first embodiment of a control motor of the invention.

FIG. 1 is a perspective view illustrating the control motor without an upper case member.

FIG. 2 is a circuit diagram of the control motor.

FIG. 3 is a front view of the control motor, the control motor being partially broken away.

FIG. 4 is a plan view illustrating the control motor without the upper case member.

FIG. 5 is an exploded view in perspective of a connection portion between a driving field effect transistor, a free-wheel diode and a motor terminal of the control motor.

FIG. 6 is a front view illustrating a connection portion between a free wheel diode and a metal plate.

FIG. 7 is a plan view illustrating the connection portion between the free wheel diode and the metal plate.

FIGS. 8, 9 and 10 are sectional views taken on VIII--VIII line, IX--IX line, X--X line of FIG. 4, respectively.

FIG. 11 is a sectional view illustrating the first embodiment of the invention where the motor is in an air conditioner.

FIG. 12 is a waveform chart for explaining an actuation of the motor of the first embodiment.

FIGS. 13 to 16 are frequency characteristic views illustrating radio noise by comparing first and second comparison example with the first embodiment.

FIGS. 17 to 28 illustrate other embodiments.

FIG. 17 (a) is a front view illustrating a second embodiment in which another unit is equipped with the motor of the invention.

FIG. 17 (b) is a bottom view illustrating the second embodiment.

FIG. 18 is a front view illustrating a third embodiment in which a radiator is equipped with the motor of the invention.

FIG. 19 is a vertical sectional view illustrating the motor of a fourth embodiment.

FIG. 20 is a vertical sectional view illustrating a fifth embodiment.

FIGS. 21 to 22 are sectional views illustrating a portion installing a lower case member in a motor yoke in embodiments six and seven.

FIG. 23 is a sectional view illustrating a portion installing a switching element in the printed circuit board in an eighth embodiment.

FIGS. 24 to 26 are sectional views illustrating portions installing the lower case members and the print-circuit boards in ninth, tenth and eleventh embodiments, respectively.

FIGS. 27 and 28 are sectional views illustrating portions installing the lower case member and the motor yoke in twelfth and thirteenth embodiments, respectively.

FIG. 29 is a perspective view illustrating a fan device equipped with a conventional motor, the fan device being partially broken away.

FIG. 30 is a perspective view, on an enlarged scale, of a portion of the conventional fan device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to drawings, a first embodiment of the invention is explained.

FIG. 2 is a circuit diagram showing a control motor comprising an integrated direct current motor and speed control circuit, which is referred to as a smart motor. The smart motor 1 is loaded into a vehicle and is used to drive a fan of a vehicle air conditioner. The smart motor 1 provides the speed control circuit which controls its rotational speed by means of receiving a direct current voltage supplied by a battery 2 in the vehicle and a motor rotation command signal generated from an electronic control unit (ECU).

A positive pole of the battery 2 whose negative pole is grounded is connected with apositive brush 7 of the directcurrent motor 5 via apower input terminal 46, aninductance coil 4, and amotor terminal 28. Anelectrolytic condenser 6 is connected between the battery side of theinductance coil 4 and aground line GND 43 to compose aLC filter circuit 8 of a power input portion. Anegative brush 12 of the directcurrent motor 5 is connected with a drain D of a driving power MOS field effect transistor 9 (hereinafter referred to as a driving FET 9) via themotor terminal 27. A source S of the driving FET 9 is connected with the ground line GND and is connected with a negative pole of the battery 2 via themotor terminal 27. The negative pole of the battery 2 is grounded. The driving FET 9 acts as a switching element which switches on and off a current flowing in the directcurrent motor 5. A gate G of the drivingFET 9 is connected with a motorcontrol signal converter 10. In the motorcontrol signal converter 10, a gate signal whose pulse width is modulated is outputted to the drivingFET 9 according to the motor rotation number command signal generating from theelectronic control unit 3 provided outside the smart motor 1. In FIG. 2 a field magnet is abbreviated.

Thepositive brush 7 and thenegative brush 12 of the directcurrent motor 5 are connected via a free-wheel diode 11 (hereinafter referred to as a FW diode 11). Thenegative brush 12 is connected with an anode of theFW diode 11. A cathode of theFW diode 11 is connected with thepositive brush 7 via themotor terminal 28. A high capacityelectrolytic condenser 13 is connected between the cathode of theFW diode 11 and the ground line GND.

An actuation of the speed control circuit of the smart motor 1 is briefly explained. When the electronic control unit (ECU) 3 provided outside the smart motor 1 sends the motor rotation number command signal to the motorcontrol signal converter 10, the motorcontrol signal converter 10 sends the gate signal whose pulse width is modulated (PWM) to the drivingFET 9. The drivingFET 9 controls the rotational speed of the directcurrent motor 5 by means of chopping the current flowing from the battery 2 and changing the voltage applied to the armature of the directcurrent motor 5. When the drivingFET 9 is OFF, the armature current flows through theFW diode 11.

In a first embodiment the above speed control circuit is formed integral with the directcurrent motor 5, so that various noises which accompany switching of the high current are reduced.

FIG. 3 is a front view of the smart motor 1 of the first embodiment, the smart motor 1 partially broken away. FIG. 4 is a plan view of the smart motor 1. FIG. 1 is a perspective view of the smart motor 1. in which an upper case body is removed.

As illustrated in FIG. 3 the directcurrent motor 5 is composed of atubular motor yoke 21, apermanent magnet segment 22 anarmature 23, acommutator 24, anoutput shaft 25, and anend face plate 26 covering an upper face of themotor yoke 21. Theend face plate 26 is composed of aconnector portion 26A and aplate portion 26B made of a resin. Themotor terminals 27 and 28 made of a metal plate penetrate theconnector potion 26A, so that theconnector portion 26A is molded. Pigtails of brushes housed in a brush holder are connected with themotor terminals 27 and 28, respectively.

Amotor holder 32 having a flange shape and formed of a steel plate is fixedly provided at an outer periphery of themotor yoke 21. Themotor holder 32 is a metallic fitting for installing the smart motor 1 in the vehicle air conditioner. As illustrated in FIG. 4, threemotor installing holes 33 are provided in themotor holder 32. As illustrated in FIG. 3, a substantially annularlower case member 34 is installed on themotor holder 32. A substantially umbrella-shapedupper case member 35 is fixed on thelower case member 34 by ascrew 36 to cover an upper part of thelower case member 34. Thelower case member 34 and theupper case member 35 are formed by means of an aluminum die cast or a press. The speed control circuit controlling the rotational speed of the directcurrent motor 5 is incorporated into an annular space enclosed byupper case member 35, thelower case member 34 and an outside peripheral face of theend face plate 26. That is, as illustrated in FIG. 1 a substantially annular printedcircuit board 40 is fixed in an upper face of thelower case member 34 by ascrew 37.

As illustrated in FIG. 1, the drivingFET 9 and theFW diode 11 are soldered and installed upright on the printedcircuit board 40 provided near themotor terminal 27 and 28, respectively. In the meanwhile,projection portions 41 and 42 projecting upward like a wall are formed integrally with thelower case member 34. Radiation fins of two of the drivingFET 9 and theFW diode 11 are closely contacted with theprojection portions 41 and 42 via an insulation plate such as a thin mica plate and are screwed in theprojection portions 41 and 42 by a screw. Two of the power MOSFET are connected in parallel with each other because the drivingFET 9 switches the high current of more than 30 A.

Power input terminals 46 and 47, illustrated in FIG. 4, are adapted to be connected with the battery 2 by alead wire 43 which is caulked to be connected with thepower input terminals 46 and 47 and is soldered in theterminals 46 and 47 (see FIG. 2).

FIG. 5 is an exploded view in perspective of a connection portion between the driving FET9 and themotor terminals 27 and 28.

Themotor terminals 27 and 28 are composed of plate-shaped male connectors and are provided in theend face plate 26 in such a state that the connection portion of themotor terminals 27 and 28 project upward. The driving FET9 is soldered upright on the printedcircuit board 40. A radiation fin 9a acting as the radiation portion of the driving FET9 is electrically common to the drain D. The radiation fin 9a and themotor terminal 27 are connected by afemale connector 51 having a L-shaped conductor. That is, themotor terminal 27 acting as the male connector is equipped with thefemale connector 51, so that an L-shaped conductor portion of thefemale connector 51 is positioned in the radiation fin 9a of the driving FET9 provided on the printedcircuit board 40 screwed on thelower case member 34. The L-shaped conductor and the radiation fin are closely contacted integrally with each other and are screwed and fixed in theprojection 41 of thelower case member 34 by ascrew 53 via the thin mica plate (not illustrated), so that thefemale connector 51 and the drivingFET 9 are fixed and themotor terminal 27 and the driving FET9 are electrically connected with each other (see FIG. 5).

Themotor terminal 28 is the same male connector as above mentionedterminal 27. Themotor terminal 28 is equipped with thefemale connector 52 fixed on the printedcircuit board 40 from upward, so that themotor terminal 28 and apattern 56 provided on the print-circuit board 40 are electrically connected with each other.

FIG. 6 is a front view illustrating a connection portion between theFW diode 11 and themetal plate 45. FIG. 7 is a plan view illustrating the above connection portion. Aradiation fin 11a of theFW diode 11 is electrically common to a cathode terminal. Themetal plate 45 is closely contacted with theradiation fin 11a and is installed integrally with theprojection 42 of thelower case member 34 by a screw. In themetal plate 45 which is provided upright on the printedcircuit board 40, theprojection 55 provided in a lower end of themetal plate 45 is inserted into a through-hole conductor of the printedcircuit board 40 and is soldered therewith, so that theprojection 55 is fixed in the printedcircuit board 40 and is connected with thepattern 56. As a result thereof, themetal plate 45 is connected with the high-capacityelectrolytic condensers 13 by thepatterns 56.

FIGS. 8 to 10 are sectional views illustrating a mutual installation of themotor holder 32, thelower case member 34, theupper case member 35 and the printedcircuit board 40. FIG. 8 is a sectional view taken taken on line VIII--VIII of FIG. 4. FIG. 9 is a sectional view taken on line IX--IX. FIG. 10 is a sectional view taken on line X--X.

As illustrated in FIG. 8, the through-hole conductor 58 conducting to aground pattern 57 is provided in the printedcircuit board 40. The print-circuit board 40 is screwed and installed in thelower case member 34 formed of the aluminium die cast by thescrew 37 inserted into the through-hole conductor 58. As a result thereof, thelower case member 34 is connected electrically to theground pattern 57 by thescrew 37.

As illustrated in FIG. 9, theupper case member 35 is installed in thelower case member 34 by thescrew 36. A through-hole conductor 59 inserting thescrew 36 is provided in the printedcircuit board 40 so as to conduct to theground pattern 57. Thescrew 36 is screwed into a screw hole of thelower case member 34 via the through-hole conductor 59 from above theupper case member 35. Theupper case member 35 is screwed in thelower case member 34 by thescrew 36. As a result thereof, the upper and thelower case members 35 and 34 are kept conducting electrically to theground pattern 57 of the print-circuit board 40.

As illustrated in FIG. 10, further, thelower case member 34 is installed in themotor holder 32 to be formed integral with themotor holder 32 by thescrew 60 which is inserted into ahole 61 of themotor holder 32 from below and is screwed into the screw hole provided in a bottom of thelower case member 34. The, the bottom of thelower case member 34 and a top of themotor holder 32 are closely contacted with each other so that themotor holder 32 forming a part of the directcurrent motor 5 is kept conducting electrically to thelower case member 34 by thescrew 60.

As a result thereof, themotor holder 32, thelower case member 34 and theupper case member 35 are installed in theground pattern 57 of the printedcircuit board 40 to conduct electrically to theground pattern 57.

FIG. 11 is a sectional view illustrating the installation of the smart motor 1 constructed as above in an air conditioner. The smart motor 1 is installed in aduct unit 65 and thefan 66 is installed in theoutput shaft 25 by a screw (not illustrated) inserted into themotor installation hole 33 of themotor holder 32. The speed control circuit provided on the printedcircuit 40 provided between theupper case member 35 and themotor holder 32 is positioned in a narrow space between thefan 66 and the directcurrent motor 5 spaces. An air current blown by thefan 66 is also exposed to theupper case member 35, resulting in a greater cooling effect of theupper case member 35.

In accordance with the above structure, an operation of the first embodiment is explained.

FIG. 12 is a waveform chart illustrating the current of various portions of the speed control circuit generated by the switching of the driving FET9. An armature current becomes a high current of approximately 30 A because a voltage of the battery 2 is 12 V in the blower motor with an output of 300 W, for example. The high current flows in current loops α and γ leading to the driving FET9 when the driving FET9 is ON and flows in current loops β and δ leading to the FW diode when the driving FET9 is OFF. Accordingly, the step-shaped space high current flows in the respective current loop in accordance with ON and OFF of the driving FET9, so that a resonance by a float inductance and a float capacitance of the respective current loop generates a high frequency oscillation and a spike-shaped oscillation voltage between apower line 44 tB and aground line 44 GND when the current is switched (see FIG. 2).

The above high frequency oscillation of voltage and current has a frequency component of the radio frequency and causes a conducted noise exerting an influence on other apparatuses via electric wires and a radiated noise radiating a harmful electromagnetic wave. In the embodiment an operation of reducing the radio noise is explained.

As illustrated in FIG. 5, in the first embodiment the driving FET9 is provided near themotor terminal 27, and the driving FET9 and and themotor terminal 27 are connected directly with each other by thefemale connector 51. TheFW diode 11 is also disposed near the motor terminal and 28 (see FIG. 4). The current loops in which the high frequency oscillation current flows, namely the current loops α and γ leading to the driving even if the high frequency oscillation generates in the current when the driving FET9 is switched, the frequency of the high frequency oscillation current is low. Accordingly, the four current loops act as antennas to reduce the energy of the radiated electromagnetic wave and the radio noise.

The small geometrical shapes of the four current loops decreases the float inductance of the current loop, thereby resulting in decreasing the high-frequency oscillation current.

Further, because the driving FET9 is connected directly with themotor terminal 27 by the female connector 51 (see FIG. 5), the float inductance by a connection between themotor terminal 27 and the drain terminal of the driving FET9 is extremely small. Accordingly, the oscillation voltage and current of the voltage between the drain and the source generated by the float inductance and the float capacitance between the drain and the source of the driving FET9 become low and the energy of the high frequency oscillation decreases, thus reducing the radio noise.

FIGS. 13 and 14 are characteristic views illustrating an effect which the first embodiment produced on the decrease of the radiated noise. FIG. 13 illustrates the radio noise in a first comparison example in which a connection of themotor terminals 27 and 28 and the speed control circuit is long without using thefemale connector 51 and 52. FIG. 14 illustrates the radio noise in the first embodiment of the invention in which themotor terminals 27 and 28 are connected directly with the driving FET9. A value of the radio noise was measured by means of an antenna located at intervals of 1 m from the smart motor 1.

The above two views shows that there is a great decrease of substantially 10 dB in the radio noise in a frequency range of 0.02 to 0.8 MHz.

FIG. 15 illustrates the radio noise in a third comparison example in which themotor holder 32 is not grounded. FIG. 16 illustrates the radio noise in the first embodiment in which themotor holder 32 is grounded. Grounding themotor holder 32 results in a decrease of the radio noise in the frequency range of 0.2 to 2 MHz.

As illustrated in FIG. 2, in the first embodiment theLC filter circuit 8 is provided in the power input portion and the high capacityelectrolytic condenser 13 is provided between the cathode side of theFW diode 11 and theground line 43 GND.

The high capacityelectrolytic condenser 13 controls a spike voltage and absorbs a counter-electromotive force of the directcurrent motor 5 when the driving FET9 is switched, thereby controlling generation of the various noises. Also, theLC filter circuit 8 controls the radio noise conducting outside theLC filter circuit 8 via an wire connected with the battery 2 by means of acting with theelectrolytic condenser 13.

TheLC filter circuit 8 provides the inductance coil only on a side of a non-ground line 44 (or the power line 44), therefore an electric potential of the ground line GND provided inside the speed control circuit is stabilized and the radio noise is decreased.

The operation of reducing the radio noise was explained above. The first embodiment has the following advantage besides the above operation. As illustrated in FIGS. 1 and 3 in the first embodiment the aluminium die cast is used as thelower case member 34 supporting the printedcircuit board 40 and theprojections 41 and 42 are provided in thelower case member 34 to be used as heat sinks of the driving FET9, and theFW diode 11. Thereby, the entirelower case member 34, which has a large shape and has a high heat capacity and has a large surface area acts as the heat sink, which results in a great improvement in terms of radiating the heat in comparison with heat sinks provided separately in the driving FET9, theFW diode 11. Also, the use of aluminum material, which conducts heat and electricity well, for thelower case member 35 further aids in radiating the heat.

Also, thespeed control circuit 40 including the power elements of the driving FET9 and theFW diode 11 are provided on thelower case member 34 so that the directcurrent motor 5 and the speed control circuit can be built separately. In this manner the advantage of a simplified manufacturing process is obtained.

As illustrated in FIG. 5, in the first embodiment, the male connectors are used as themotor terminals 27 and 28 and themotor terminals 27 and 28 are adapted to be connected with the speed control circuit provided on the printedcircuit board 40 by thefemale connectors 51 and 52 fixed in theFW diode 11 and the driving FET9. Thus the installation oflower case member 34 in themotor holder 32 both integrates the printedcircuit board 40, upon which is composed the speed control circuit, with the separately built directcurrent motor 5 and also connectsmale connectors 27 and 28 withfemale connectors 51 and 52. This simplifies the installation operation in that a separate connection operation is not needed. Further, disassembling the directcurrent motor 5 and the print-circuit board 40 is simplified and thelower case member 34 and the print-circuit board 40 composing the speed control circuit can be exchanged as a unit, which leads to simplified maintenance.

In the first embodiment, various considerations are given because the speed control circuit is incorporated into a narrow space between thefan 66 and the directcurrent motor 5. That is, as illustrated in FIGS. 1 and 3, the driving FET9, and theFW diode 11 are adapted to be provided upright on the printedcircuit board 40 and to be in close contact with the directcurrent motor 5, thereby reducing space.

In the first embodiment explained above, the speed control circuit is located in the narrow space between the directcurrent motor 5 and the fan 66 (see FIG. 11). However, various installation positions of the speed control circuit may be contemplated in which the smart motor 1 may be incorporated.

For example, air also travels in an axial direction along the periphery of the directcurrent motor 70 in a double intake blower motor of the second embodiment of the invention, as illustrated in FIGS. 17(a) and 17(b) and a motor for cooling a radiator of the third embodiment as illustrated in FIG. 18. Thespeed control circuit 71 is incorporated into the motor end of the reverse side of the output shaft of the directcurrent motor 70, thereby allowing an effective cooling of the control motor. Also, if aradiation fin 202 is formed in a surface of the case member of thespeed control circuit 71, the cooling effect can be further enhanced (see FIGS. 17(a) and 17(b). When thespeed control circuit 71 is provided on the motor end, it is desirable to provide a commutator in the motor end side and provide themotor terminal 72 near the motor end so as to reduce the current loop and the radio noise. In FIGS. 17(a), 17(b) and 18, numeral 73 designates the motor holder,numerals 74 and 75 designate the fans, numeral 201 designates an auxiliary fan fixedly provided in a lower face offan 74 and numeral 76 designates the radiator.

In the fourth embodiment, as illustrated in FIG. 19, a printedcircuit board 78 is incorporated into a cylindricallower case member 77 having a bottom and is installed in the motor end of the directcurrent motor 70. Thecase member 77 is formed of the aluminium die case and is provided partially with aprojection 89 having a side wall shape and is used as the heat sink of power elements of the driving FET9 andFW diode 11. Thepower elements 9 and 11 are installed upright in theprojection 89, so that a surface of the printedcircuit board 78 can be utilized effectively and so that the current loops α to δ (see FIG. 2) of the speed control circuit including the power elements can be reduced in size. This structure allows concentration of the elements having a high current.Numeral 82 designates a cover member, numeral 83 designates a screw for fixing the driving FET9 (see FIG. 19).

In a fifth embodiment, as illustrated in FIG. 20, thecase member 85 is installed in the motor end of the directcurrent motor 70 and a diameter of acase member 85 is reduced to be substantially identical with that of the directcurrent motor 70 and two layers of the print-circuit boards 86 and 87 are provided in thecase member 85. The power elements in which the high current of theFW diode 11 flows are collected in the printedcircuit board 86 of an upper layer and the speed control circuit portions of a low current signal are collected in the printedcircuit board 87 of the lower layer. Thus, the print-circuit boards 86 and 87 are provided separately in thecase member 85. The outer diameter of thecase member 85 is reduced to facilitate the loading of the smart motor in the vehicle and to decrease the size of current loops α to β of the speed control circuit which include the power elements. The radiation fin of power elements such as the driving FET9 andFW diode 11 is closely attached to theprojection 89 of thecase member 85 by thescrew 84.

If thecase members 77 and 85 are installed in the motor end of the direct current motor via thecover member 82 as in the fourth and the fifth embodiments as illustrated in FIGS. 19 and 20, respectively, and as in the sixth and seventh embodiment as illustrated in FIGS. 21 and 22, ascrew hole 96 is formed in themotor yoke 21 of the directcurrent motor 70 and thecover member 82 is screwed directly in themotor yoke 21 by thescrew 97, so that themotor yoke 21 of the directcurrent motor 70 conducts electrically to thecover member 82. In the first embodiment the through-hole conductors 58 and 59 are used to connect theground pattern 57 and thelower case member 34 on the print-circuit board 40. The use of the both structures illustrated in FIGS. 8 and 9 allows simplification of the grounding structure. An eighth embodiment, illustrated in FIG. 22, shows thecover member 82 fixed in themotor yoke 21 by arivet 98.

In the first embodiment and the fifth to the sixth embodiments the power elements, such as theFW diode 11, are provided upright on the print-circuit boards 40, 78, and 86. However, as in the ninth embodiment as illustrated in FIG. 23 steppedprojections 99 may be provided in thelower case member 34 and thecase members 77, 85 and 90 upon which to lay power elements such as the driving FET9 and theFW diode 11.

In FIGS. 1, 5, and 6, theprojections 41, 42, and 89 with which the radiation fin of the power elements such as the driving FET9 and theFW diode 11 are closely contacted are formed integrally with thecase members 34, 77, and 85, by the aluminium die cast. However, only theprojections 41, 42, and 89 may be formed of a block-shaped good conductor of heat and be closely contacted integrally with thecase members 34, 77, and 85.

In the first embodiment, as illustrated in FIGS. 8 to 10, the print-circuit board 40 is installed in thelower case member 34 by thescrew 37 and the print-circuit board 40 and thelower case member 34 are installed in theupper case member 35 by thescrew 36 and themotor holder 32 is installed in thelower case member 34 by ascrew 60. In the ninth to the eleventh embodiments, as illustrated in FIGS. 24, 25 and 26,projections 101, 102 and 103 may be provided in thelower case member 34 and be inserted into the through-hole conductors 58 and 59 and thehole 61 of themotor holder 32 and be caulked to fix the print-circuit board 40 and thelower case member 34 mutually.

In the same way, in twelfth and thirteenth embodiments, as shown in FIGS. 27 and 28,projection 104 provided in thecover member 82 may be inserted intohole 106 andprojection 105 provided in themotor yoke 21 may be inserted into ahole 107 and theprojections 104 and 105 may be caulked to fix themotor yoke 21 and thecover member 82.

As illustrated in FIG. 5, in the first embodiment the detachablefemale connectors 51 and 52 are used to connect the driving FET9 and theFW diode 11 with themotor terminals 27 and 28. However plate-shaped terminal metal fittings may be soldered and connected directly with themotor terminals 27 and 28, thereby also allowing reduction of the radio noise.

Further, themotor terminal 27 may be formed into a L-shaped member and the radiation fin 9a of the driving FET9 may be adapted to be screwed directly in themotor terminal 27.

When thefemale connectors 51 and 52 are used as the terminal metal fittings, the female connectors can be used as themotor terminals 27 and 28 and the male connectors can be used as theconnectors 51 and 52.

The control motor of the invention provides a projection which is formed integrally with the case member formed of the material which conducts heat well and is used as the heat sink of the power terminal, which results in a great deal of heat being radiated. Further, the case member performs the function of the electromagnetic shield, reducing the radio noise.

In the control motor of the invention, the entire speed control circuit, including the power elements such as the switching element, is provided on the case member, therefore assembling the speed control circuit in manufacturing and disassembing it in maintenance are easy. In the control motor, the through-hole conductor is used to conduct the ground pattern of the print-circuit board and the case member. This facilitates keeping the case member grounded. Further, this results in promoting the electromagnetic shield function of the case member, thereby reducing the radio noise.

In the control motor, the case member is kept conducting to the speed control circuit and is fixed in the direct current motor by the metallic fixing means. In the control motor, and outer shell of the direct current motor is grounded and the electromagnetic shield function is improved, reducing the radio noise.

In the control motor of the invention, the switching element and the motor terminal are connected directly by the terminal metallic fittings, therefore there is an advantage in that the geometrical shape of the current loops become small, reducing the radio noise greatly.

In the control motor in which the female and the male connectors are used as the motor terminal and the terminal metallic fittings, the direct current motor and the speed control circuit can be easily disconnected and connected while the above advantage is kept. Therefore, the direct current motor and the speed control circuit can be manufactured by means of a separate installation and the installation can be simplified. Also, separate maintenance of the direct current motors and the speed control circuit is possible.

The control motor of the invention provides the LC filter circuit having the inductance only on the non-ground line and the high capacity electrolytic condenser connected with the cathode side of the free wheel diode. Therefore, there is an advantage in that the generation and the radiation of the radio noise are reduced and the noise generating inside the speed control circuit reduces the radio noise conducting outside the LC filter circuit via the power source line.

Claims (7)

What is claimed is:

1. A control motor comprising an integrated direct current motor and speed control circuit, said speed control circuit controlling a rotational speed of said direct current motor by means of changing a voltage applied to an armature of said motor by a chopping of a switching element, said speed control circuit being composed upon a printed circuit board which is supported in said direct current motor by a case member formed of a heat-conducting material, and a radiation portion of said switching element which is in close contact with a projection formed integrally with said case member and is installed in said projection.

2. The control motor in claim 1, wherein said printed circuit board has a through-hole conductor conducting to a ground pattern and said printed circuit board is installed in said case member by a conductive metallic installing means inserted into the through-hole conductor.

3. The control motor in claim 2, wherein said case member is kept conducting electrically to said ground pattern and is fixed in a yoke of said direct current motor by a conductive metallic fixing means.

4. The control motor as defined in claims 1 or 3, wherein said case member comprises a lower case member in which said printed circuit board is fixed, and an upper case member which is formed of an electrically conductive material and covers said speed control circuit.

5. The control motor as defined in claim 1, wherein the switching element which switches on and off a current flowing in said direct current motor is provided near a motor terminal connected with a brush and fixedly installed in said direct current motor and a radiation fin of the switching element is directly connected to the motor terminal by a terminal metal fitting.

6. The control motor defined in claim 5, wherein said motor terminal is composed of either a male or a female connector and said connector is composed of either a female or the male connector corresponding to a male or a female of said motor terminal and said switching element is connected with said motor terminal by either the male or the female connector provided in said switching element.

7. The control motor as defined in claim 1, wherein said speed control circuit provides an LC filter circuit provided in a power source input portion and having an inductance only on a non-ground line side, said switching element switches on and off the current flowing to said direct current motor, a free wheel diode connected in parallel with said direct current motor, and a high capacity electrolytic condenser connected between a cathode side of said free wheel diode and the ground line.

Images